Re: 3D TV

[P3D Gabriel Jacob <jacob@xxxxxxxxxxxxxx>]

John W Roberts writes

>You're thinking of the *other* volumetric display, the intersecting IR 
>laser beams in a solid-state cube. This is the one with a big rotating
>helix (I think the one I saw in ~1995 was about 12-18 inches across), put
>in a clear box so it doesn't blow wind in your face, and *visible light*
>lasers spray voxels onto the helix as it spins. *No wonder* you thought
>the article didn't describe the system very well!  :-)   :-)   :-)
>
>[Note: yet another volumetric display technology uses a spinning flat
>phosphor screen to sweep a volume in an evacuated glass chamber, while an
>electron beam scans it.]

Yes as you mention the crystal volumetric 3D display doesn't use rotating
screens and the article in Wired refers to another technique. When Bill
Costa posted about the 3D TV, it made me think of the other volumetric
display that you mention above also. The one you mention above was done
quite a long time ago and remember reading about it in an old text book.
The book was Optoelectronic Devices And Circuits by Samuel Weber and
published by McGraw-Hill in 1964.

In it they describe the display in question. This was researched by Hughes
Research Laboratories and was accomplished by a phosphor coated mesh 
screen rotating about the veritcal axis in an evacuated glass sphere.
Simple Lissajous patterns illustrated the ease of determining line 
intersections. They then go on to describe how it could be used for
air-traffic control and how multiple colors could be introduced. It would
be interesting to know what happened with this research as the book I have
is rather dated.

In the same book there is another article that describes yet another
volumetric display but is quite different from the previous discussions.
In this one the 3 dimensional CRT uses atomic resonance. They describe
how multiple excitation of mercury vapor may lead to a true solid display.
This was done by Missle and Space Vehicle Dept., by General Electric.
One thing I might mention is that all these technologies don't rely
strictly on perspective differences but actually set out to reproduce
reality in an actual space and thus replicates 3D this way.

Gabriel





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